Method and apparatus for registering access point in wireless communication system

ABSTRACT

A method and apparatus of registering an entity of a secondary radio access technology (RAT) system in a management device of a primary RAT system in a wireless communication system is provided. The primary RAT system may be a cellular system, and the management device of the primary RAT system may be one of eNodeB (eNB), mobility management entity (MME), or a new entity. The second RAT system may be a wireless local area network (WLAN) system, and the entity of the secondary RAT system may be an access point (AP). The AP registration method may be initiated by the AP, or a general device, e.g., a multi radio access technology (RAT) device supporting a plurality of RATs.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to wireless communications, and morespecifically, to a method and apparatus for registering an access point(AP) in a wireless communication system.

2. Related Art

With the recent trend of increasing high-rate data traffic, fifthgeneration mobile communication technologies are in discussion for theirrealistic and efficient backup. One of requirements for fifth generationmobile communication technologies is the interworking betweenheterogeneous wireless communication systems, particularly between acellular system and a wireless LAN (WLAN) system. The cellular systemmay be one of a 3^(rd) generation partnership project (3GPP) long-termevolution (LTE) system, a 3GPP LTE-A (advanced) system, and an instituteof electrical and electronics engineers (IEEE) 802.16 (WiMax, WiBro)system. The WLAN system may be an IEEE 802.11 (Wi-Fi) system. Inparticular, WLAN is a wireless communication system that is commonlyused for various user equipments, and thus, the cellular-WLANinteroperation is a high-priority convergence technique. Offloading bythe cellular-WLAN interoperation may increase the coverage and capacityof the cellular system.

The arrival of the ubiquitous environment led to a sharp increase indemand for seamless services anytime, anywhere. The fifth generationmobile communication system may adopt a plurality of radio accesstechnologies (RATs) for always gaining easy access and maintainingefficient performance in any place. In other words, the fifth-generationmobile communication system may use multiple RATs in a converging mannerthrough the interoperation between heterogeneous wireless communicationsystems. Each entity in the plurality of RATs constituting afifth-generation mobile communication system may exchange informationtherebetween, and accordingly, the optimal communication system may beprovided to a user in the fifth-generation mobile communication system.Among the plurality of RATs constituting the fifth-generation mobilecommunication system, a specific RAT may operate as a primary RATsystem, and another specific RAT may operate as a secondary RAT system.That is, the primary RAT system may mainly play a role to provide acommunication system to a user in the fifth-generation mobilecommunication system, while the secondary RAT system may assist theprimary RAT system. In general, a 3GPP LTE(-A) or IEEE 802.16 cellularsystem with relatively broad coverage may be a primary RAT system, and aWi-Fi system with relatively narrower coverage may be a secondary RATsystem.

In a fifth-generation mobile communication system constituted of aplurality of RATs, a primary RAT system needs to grasp the entities of asecondary RAT system that operates within its own coverage. For example,in case that a primary RAT system is a cellular system, and a secondaryRAT system is a Wi-Fi system, a cellular node such as an eNodeB (eNB),mobility management entity (MME), or new cellular entity need be awareof which access points (APs) are in operation within its coverage.Accordingly, when sensing a secondary RAT system entity, a userequipment need let the cellular node know AP information. Further, aneed exists for a method for efficiently registering an AP in thecellular node based on the AP information.

SUMMARY OF THE INVENTION

The present invention provides a method and apparatus for registering anAP in a wireless communication system. The present invention provides amethod for transmitting, by the AP, information on the AP to a cellularnode through a Wi-Fi radio interface with a general device or a cellularradio interface of the general device. Further, the present inventionprovides a method for transmitting, by a general device, information onan AP, which has been sensed by the general device through a Wi-Fi radiointerface, to a cellular node.

In an aspect, a method of registering, by a multi radio accesstechnology (RAT) device supporting a plurality of RATs, an entity of asecondary RAT system in a management device of a primary RAT system in awireless communication system is provided. The method includes receivinga request for registration of an entity of a secondary RAT system fromthe entity of the secondary RAT system, if the request for registrationis authorized, determining whether the entity of the secondary RATsystem is included in a list of entities of the secondary RAT systemregistered in a management device of a primary RAT system, if it isdetermined that the entity of the secondary RAT system is not includedin the list, transmitting a registration request message includinginformation on the entity of the secondary RAT system to the managementdevice of the primary RAT system, receiving a registration responsemessage including a result of the request for registration of the entityof the secondary RAT system from the management device of the primaryRAT system, and transmitting a registration result parameter includingthe result of the registration of the entity of the secondary RAT systemto the entity of the secondary RAT system.

The request for registration of the entity of the secondary RAT systemmay be an access point (AP) registration request flag included in abeacon frame, a probe response frame, an authentication response frame,or an association response frame.

The request for registration of the entity of the secondary RAT systemmay be a newly defined AP registration request frame.

The information on the entity of the secondary RAT system may include atleast one of a media access control (MAC) address of the entity of thesecondary RAT system, a service set identifier (SSID) of the entity ofthe secondary RAT system, a position of the entity of the secondary RATsystem, an homogeneous extended service set ID (HESSID) of the entity ofthe secondary RAT system, whether of the entity of the secondary RATsystem can be used by a limited user, or information on a frequencychannel used by the entity of the secondary RAT system.

The result of the request for registration of the entity of thesecondary RAT system may be one of ‘already registered,’ ‘success,’ or‘failure’. If the result of the request for registration of the entityof the secondary RAT system is ‘failure,’ the registration resultparameter may further include cause for the result of the request forregistration.

The primary RAT system may be a cellular system, and the managementdevice of the primary RAT system may be one of an eNodeB (eNB), amobility management entity (MME), or a new entity of the cellularsystem.

The secondary RAT system may be a Wi-Fi system, and the entity of thesecondary RAT system may be an AP.

In another aspect, a method of registering, by a multi radio accesstechnology (RAT) device supporting a plurality of RATs, an entity of asecondary RAT system in a management device of a primary RAT system in awireless communication system is provided. The method includes receivinga first frame from an entity of a secondary RAT system. A request forregistration of the entity of the secondary RAT system and informationon the entity of the secondary RAT system are encapsulated in the firstframe. The method further include transmitting a registration requestmessage including the request for registration of the entity of thesecondary RAT system and the information on the entity of the secondaryRAT system to a management device of a primary RAT system, receiving aregistration response message including a result of the request forregistration of the entity of the secondary RAT system from themanagement device of the primary RAT system, and transmitting a secondframe to the entity of the secondary RAT system, wherein the result ofthe request for registration of the entity of the secondary RAT systemis encapsulated in the second frame.

The first frame may include a field indicating that the first frame istransmitted to the management device of the primary RAT system.

The registration response message may indicate that the registrationresponse message is transmitted to the entity of the secondary RATsystem.

In another aspect, a method of registering, by a multi radio accesstechnology (RAT) device supporting a plurality of RATs, an entity of asecondary RAT system in a management device of a primary RAT system in awireless communication system is provided. The method includesdiscovering an entity of a secondary RAT system through scanning,transmitting a registration request message including information on theentity of the secondary RAT system to a management device of a primaryRAT system, and receiving a registration response message including aresult of the request for registration of the entity of the secondaryRAT system from the management device of the primary RAT system.

The method may further include transmitting a request for a list ofentities of a secondary RAT system registered in the management deviceof the primary RAT system to the management device of the primary RATsystem.

In a convergence communication system of a cellular system and a Wi-Fisystem, a cellular node may efficiently grasp a Wi-Fi system entity thatoperates within its coverage.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cellular system.

FIG. 2 shows a structure of a radio frame in 3GPP LTE.

FIG. 3 shows a wireless local area network (WLAN) system.

FIG. 4 shows an example of a frame structure of IEEE 802.11.

FIG. 5 shows an example of a scenario of a converged communicationsystem of a cellular system and a Wi-Fi system.

FIG. 6 shows an example of a scenario to which an AP registration methodaccording to an embodiment of the present invention may be applied.

FIG. 7 shows an AP registration method according to an embodiment of thepresent invention.

FIG. 8 shows an AP registration method according to another embodimentof the present invention.

FIG. 9 shows an example of an AP registration request frame structureaccording to an embodiment of the present invention.

FIG. 10 shows an AP registration method according to another embodimentof the present invention.

FIG. 11 shows an AP registration method according to another embodimentof the present invention.

FIG. 12 shows an AP registration method according to another embodimentof the present invention.

FIG. 13 is a block diagram showing wireless communication system toimplement an embodiment of the present invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

A technology below can be used in a variety of wireless communicationsystems, such as code division multiple access (CDMA), frequencydivision multiple access (FDMA), time division multiple access (TDMA),orthogonal frequency division multiple access (OFDMA), and singlecarrier frequency division multiple access (SC-FDMA). CDMA can beimplemented using radio technology, such as universal terrestrial radioaccess (UTRA) or CDMA2000. TDMA can be implemented using radiotechnology, such as global system for mobile communications(GSM)/general packet radio service (GPRS)/enhanced data rates for GSMevolution (EDGE). OFDMA can be implemented using radio technology, suchas IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, or EvolvedUTRA (E-UTRA). IEEE 802.16m is the evolution of IEEE 802.16e, and itprovides a backward compatibility with an IEEE 802.16e-based system.UTRA is part of a universal mobile telecommunications system (UMTS). 3rdgeneration partnership project (3GPP) long term evolution (LTE) is partof evolved UMTS (E-UMTS) using evolved-UMTS terrestrial radio access(E-UTRA), and it adopts OFDMA in downlink (DL) and SC-FDMA in uplink(UL). LTE-A (advanced) is the evolution of 3GPP LTE.

3GPP LTE(-A) and IEEE 802.11 are chiefly described as an example inorder to clarify the description, but the technical spirit of thepresent invention is not limited to 3GPP LTE(-A) and IEEE 802.11.

FIG. 1 shows a cellular system.

Referring to FIG. 1, the cellular system 10 includes one or more basestations (BSs) 11. The BSs 11 provide communication services torespective geographical areas (in general called ‘cells’) 15 a, 15 b,and 15 c. Each of the cells can be divided into a number of areas(called ‘sectors’). A user equipment (UE) 12 can be fixed or mobile andmay be referred to as another terminology, such as a mobile station(MS), a mobile terminal (MT), a user terminal (UT), a subscriber station(SS), a wireless device, a personal digital assistant (PDA), a wirelessmodem, or a handheld device. In general, the BS 11 refers to a fixedstation that communicates with the UEs 12, and it may be referred to asanother terminology, such as an evolved-NodeB (eNB), a base transceiversystem (BTS), or an access point.

The UE generally belongs to one cell. A cell to which a UE belongs iscalled a serving cell. A BS providing the serving cell withcommunication services is called a serving BS. A wireless communicationsystem is a cellular system, and so it includes other cells neighboringa serving cell. Other cells neighboring the serving cell are calledneighbor cells. A BS providing the neighbor cells with communicationservices is called as a neighbor BS. The serving cell and the neighborcells are relatively determined on the basis of a UE.

This technology can be used in the downlink (DL) or the uplink (UL). Ingeneral, DL refers to communication from the BS 11 to the UE 12, and ULrefers to communication from the UE 12 to the BS 11. In the DL, atransmitter may be part of the BS 11 and a receiver may be part of theUE 12. In the UL, a transmitter may be part of the UE 12 and a receivermay be part of the BS 11.

FIG. 2 shows a structure of a radio frame in 3GPP LTE. It may bereferred to Section 4 of 3GPP TS 36.211 V8.2.0 (2008-03).

Referring to FIG. 2, the radio frame includes 10 subframes, and onesubframe includes two slots. The slots in the radio frame are numberedby #0 to #19. A transmission time interval (TTI) is a scheduling unitfor a data transmission. In 3GPP LTE, one TTI may be identical with atime taken for transmitting one subframe. A radio frame may have alength of 10 ms, a subframe may have a length of 1 ms, and a slot mayhave a length of 0.5 ms.

One slot includes a plurality of orthogonal frequency divisionmultiplexing (OFDM) symbols in a time domain and a plurality ofsubcarriers in a frequency domain. Since 3GPP LTE uses OFDMA indownlink, the OFDM symbols are used to express a symbol period. The OFDMsymbols may be called by other names depending on a multiple-accessscheme. For example, when a single carrier frequency division multipleaccess (SC-FDMA) is in use as an uplink multi-access scheme, the OFDMsymbols may be called SC-FDMA symbols. A resource block (RB), a resourceallocation unit, includes a plurality of continuous subcarriers in aslot. The structure of the radio frame is merely an example. Namely, thenumber of subframes included in a radio frame, the number of slotsincluded in a subframe, or the number of OFDM symbols included in a slotmay vary.

3GPP LTE defines that one slot includes seven OFDM symbols in a normalcyclic prefix (CP) and one slot includes six OFDM symbols in an extendedCP.

FIG. 3 shows a wireless local area network (WLAN) system.

The WLAN system may also be referred to as a Wi-Fi system. Referring toFIG. 3, the WLAN system includes one access point (AP) 20 and aplurality of stations (STAs) 31, 32, 33, 34, and 4). The AP 20 may belinked to each STA 31, 32, 33, 34, and 40 and may communicate therewith.The WLAN system includes one or more basic service sets (BSSs). The BSSis a set of STAs that may be successfully synchronized with each otherand may communicate with each other, and does not mean a specificregion.

An infrastructure BSS includes one or more non-AP stations, APs thatprovide a distribution service (DS), and a DS that links a plurality ofAPs with each other. In the infrastructure BSS, an AP manages non-APSTAs of the BSS. Accordingly, the WLAN system shown in FIG. 3 mayinclude an infrastructure BSS. In contrast, an independent BSS (IBSS) isa BSS that operates in ad-hoc mode. The IBSS does not include an AP andthus lacks a centralized management entity. That is, in the IBSS, thenon-AP STAs are managed in a distributed manner. The IBSS may have allthe STAs constituted of mobile STAs and is not allowed to access thedistribution system, thus achieving a self-contained network.

The STA is random functional medium that includes a physical layerinterface for a wireless medium and an media access control (MAC))observing IEEE 802.11 standards, and in its broader concepts, itincludes both the AP and non-AP station.

The non-AP STA is an STA, not an AP. The non-AP STA may also be referredto as a mobile terminal, a wireless device, a wireless transmit/receiveunit (WTRU), a user equipment (UE), a mobile station (MS), a mobilesubscriber unit or simply as a user. Hereinafter, for ease ofdescription, the non-AP STA denotes an STA.

The AP is a functional entity that provides access to a distributionsystem via a wireless medium for an STA associated with the AP. In theinfrastructure BSS including an AP, communication between STAs isbasically done via an AP, but in case a direct link is established,direct communication may be achieved between STAs. The AP may also bereferred to as a central controller, a base station (BS), a NodeB, abase transceiver system (BTS), or a site controller.

A plurality of infrastructure BSSs may be linked with each anotherthrough a distribution system. The plurality of BSSs linked with eachanother is referred to as an extended service set (ESS). The APs and/orSTAs included in the ESS may communicate with each other, and in thesame ESS, an STA may move from one BSS to another, while in seamlesscommunication.

FIG. 4 shows an example of a frame structure of IEEE 802.11.

A frame of IEEE 802.11 includes a set of fields in a fixed order.Referring to FIG. 4, the frame of IEEE 802.11 includes a frame controlfield, a duration/ID field, an address 1 field, an address 2 field, anaddress 3 field, a sequence control field, an address 4 field, a qualityof service (QoS) control field, an HT control field, a frame body field,and a frame check sequence (FCS) field. Among the fields listed above,the frame control field, the duration/ID field, the address 1 field, andthe FCS field constitute a minimum IEEE 802.11 frame format, and may beincluded in all IEEE 802.11 frames. The address 2 field, the address 3field, the sequence control field, the address 4 field, the QoS controlfield, the HT control field, and the frame body field may be includedonly in a specific frame type.

The frame control field may include various subfields. The duration/IDfield may be 16 bits in length. The address field may include a basicservice set identifier (BSSID), a source address (SA), a destinationaddress (DA), a transmitting STA address (TA), and a receiving STAaddress (RA). In the address field, different fields may be used forother purposes according to a frame type. The sequence control field canbe used when fragments are reassembled or when an overlapping frame isdiscarded. The sequence control field may be 16 bits, and may includetwo subfields indicating a sequence number and a fragment number. TheFCS field can be used to check an error of a frame received by astation. The FCS field may be a 32-bit field including a 32-bit cyclicredundancy check (CRC). An FCS can be calculated across the frame bodyfield and all fields of a media access control (MAC) header.

The frame body field may include information specified for an individualframe type and subtype. That is, the frame body field carries high-leveldata from one station to another station. The frame body field can alsobe called a data field. The frame body field can be variously changed inlength. A minimum length of the frame body field may be zero octet. Amaximum length of the frame body field may be determined by a total sumof a maximum length of a MAC service data unit (MSDU), a length of amesh control field, and an overhead for encryption or a total sum of amaximum length of an aggregated MSDU (A-MSDU) and an overhead forencryption. The data frame includes high-level protocol data of theframe body field. The data frame may always include the frame controlfield, the duration/ID field, the address 1 field, the address 2 field,the address 3 field, the sequence control field, the frame body field,and the FCS field. A presence of an address 4 field may be determined bya configuration of a ‘To DS’ subfield and a ‘From DS’ subfield in theframe control field. Another data frame type can be categorizedaccording to a function.

A management frame may always include the frame control field, theduration/ID field, the address 1 field, the address 2 field, the address3 field, the sequence control field, the frame body field, and the FCSfield. Data included in the frame body field generally uses afixed-length field called a fixed field and a variable-length fieldcalled an information element. The information element is avariable-length data unit.

The management frame can be used for various purposes according to asubtype. That is, a frame body field of a different subtype includesdifferent information. A beacon frame reports an existence of a network,and takes an important role of network maintenance. The beacon framecorresponds to a parameter which allows a mobile station to participatein the network. In addition, the beacon frame is periodicallytransmitted so that the mobile station can scan and recognize thenetwork. A probe request frame is used to scan an IEEE 802.11 network inwhich the mobile station exists. A probe response frame is a responsefor the probe request frame. An authentication request is used so thatthe mobile station requests an access point to perform authentication.An authentication response frame is a response for the authenticationrequest frame. A de-authentication frame is used to finish anauthentication relation. An association request frame is transmitted sothat the mobile station participates in the network when the mobilestation recognizes the compatible network and is authenticated. Anassociation response frame is a response for the association requestframe. A de-association frame is used to finish an association relation.

Three states may exist according to an authentication and associationprocedure in IEEE 802.11. Table 1 below shows the three states of IEEE802.11.

TABLE 1 Authentication Association State 1 X X State 2 ◯ X State 3 ◯ ◯

To transmit a data frame, a device must perform the authentication andassociation procedure with respect to a network. In Table 1, a procedureof transitioning from the state 1 to the state 2 can be called theauthentication procedure. The authentication procedure can be performedin such a manner that one device acquires information of a differentdevice and authenticates the different device. The information of thedifferent device can be acquired by using two methods, i.e., a passivescanning method for acquiring information of a different node byreceiving a beacon frame and an active scanning method for acquiring theinformation of the different device by transmitting a probe requestmessage and receiving a probe response message received in responsethereto. The authentication procedure can be complete by exchanging anauthentication request frame and an authentication response frame.

In Table 1, a procedure of transitioning from the state 2 to the state 3can be called the association procedure. The association procedure canbe complete when two devices exchange the association request frame andthe association response frame upon completion of the authenticationprocedure. An association ID can be allocated by the associationprocedure.

FIG. 5 shows an example of a scenario of a converged communicationsystem of a cellular system and a Wi-Fi system.

It is assumed in FIG. 5 that the cellular system operates as a primaryRAT system of the converged communication system, and the Wi-Fi systemoperates as a secondary RAT system of the converged communicationsystem. Further, the cellular system may be a 3GPP LTE(-A) system.Hereinafter, for ease of description, it is assumed that the primary RATsystem of the converged communication system is a 3GPP LTE(-A) system,and the secondary RAT system of the communication system is an IEEE802.11 system, i.e., a Wi-Fi system. However, embodiments of the presentinvention are not limited thereto.

Referring to FIG. 5, there are a plurality of general devices 61, 62,63, 64, and 65 in the coverage of the cellular base station 50. Each ofthe general devices 61, 62, 63, 64, and 65 may be a user equipment in acellular system. The cellular base station 50 may communicate with eachof the general devices 61, 62, 63, 64, and 65 via a cellular radiointerface. For example, the cellular base station 50 may perform voicecall communication with each of the general devices 61, 62, 63, 64, and65 or may control access of each general device 61, 62, 63, 64, and 65to a Wi-Fi system.

The cellular base station 50 is connected to a serving gateway(S-GW)/mobility management entity (MME) 70 through a cellular systeminterface. The MME contains a user equipment's access information orinformation on a user equipment's capability, and such information maybe mainly used for mobility management. The MME is in charge of acontrol plane. The S-GW is a gateway having an E-UTRAN as an end point.The S-GW is in charge of a user plane. The S-GW/MME 70 is connected to apacket data network (PDN) gateway (P-GW) 71 and an home subscriberserver (HSS) 72 through the cellular system interface. The PDN-GW is agateway having a PDN as an end point.

The P-GW 71 and the HSS 72 are connected to a 3GPP access authenticationauthorization (AAA) server 73 through the cellular system interface. TheP-GW 71 and the 3GPP AAA server 73 may be connected to an evolved packetdata gateway (e-PDG) 74 through the cellular system interface. The e-PDG74 may be included only in untrusted non-3GPP access. The e-PDG 74 maybe connected to a WLAN access gateway (WAG) 75. The WAG 75 may be incharge of a P-GW in a Wi-Fi system.

Meanwhile, a plurality of APs 81, 82, and 83 may be present in thecoverage of the cellular base station 50. Each of the APs 81, 82, and 83may have coverage which is shorter than that of the cellular basestation 50. Each of the APs 81, 82, and 83 may communicate with generaldevices 61, 62, and 63 that are present in its coverage through a Wi-Firadio interface. In other words, the general devices 61, 62, and 63 maycommunicate with the cellular base station 50 and/or APs 81, 82, and 83.Communication methods of the general devices 61, 62, and 63 are asfollows:

1) Cellular/Wi-Fi simultaneous radio transmission: the general device 61may perform high-speed data communication with the AP 81 through a Wi-Firadio interface while communicating with the cellular base station 50through a cellular radio interface.

2) Cellular/Wi-Fi user plane automatic shift: the general device 62 maycommunicate with one of the cellular base station 50 and the AP 82 byuser plane automatic shift. At this time, the control plane may bepresent in both the cellular system and the Wi-Fi system or only in thecellular system.

3) Terminal cooperative transmission: the general device 64 operating asa source device may directly communicate with the cellular base station50 through a cellular radio interface or may indirectly communicate withthe cellular base station 50 through a general device 65 operating as acooperative device. That is, the cooperative device 65 may assist thesource device 64 so that the source device 64 may indirectly communicatewith the cellular base station 50 through itself. The source device 64and the cooperative device 65 communicate with each other through aWi-Fi radio interface.

4) Wi-Fi-based cellular link control mechanism: the AP 83 may perform acellular link control mechanism such as paging or location registrationof a network for the cellular general device 63. The general device 63is not directly connected to the cellular base station 50 and maydirectly communicate with the cellular base station 50 thorough the AP83.

Each of the APs 81, 82, and 83 is connected to the WAG 75 through aWi-Fi system interface.

A method for a cellular node obtaining information on an AP through anAP registration procedure according to an embodiment of the presentinvention is described. The AP registration procedure according to anembodiment of the present invention may be generally classified into anAP registration procedure initiated by an AP (AP initiated APregistration) and an AP registration procedure initiated by a generaldevice such as a user equipment or a multi radio access technology(multi-RAT) device (device initiated AP registration). Hereinafter, thecellular node may be a new entity of a cellular system, eNB, or MME.Further, the general device may also be referred to as a user equipmentor multi-RAT device.

FIG. 6 shows an example of a scenario to which an AP registration methodaccording to an embodiment of the present invention may be applied.Referring to FIG. 6, a general device communicates with a base stationthrough a cellular radio interface and with an AP through a Wi-Fi radiointerface. The base station is connected to an MME or a new APmanagement entity. The AP is connected to a WAG.

First, an AP registration procedure initiated by an AP according to anembodiment of the present invention is described.

FIG. 7 shows an AP registration method according to an embodiment of thepresent invention. The embodiment described in FIG. 7 indicates an APregistration method by which an AP requests its registration using anexisting Wi-Fi system frame as is.

In step S100, a multi-RAT device transmits a probe request frame to anAP. In step S101, the AP transmits to the multi-RAT device a proberesponse frame including an AP registration request flag, as a responseto the probe request frame. The AP registration request flag indicates arequest for AP registration to a cellular node. When indicating the APregistration request, a value of the AP registration request flag maybe 1. The AP registration request flag is merely an example, and otherparameters may be included in the probe response frame in order toindicate the AP registration request. The probe response frame mayfurther include information on whether a re-transmission procedurerequest is made as the AP registration request fails.

Further, although in the embodiment described in FIG. 7 the AP requestsits registration using a probe response frame, the present invention isnot limited thereto. The AP may transmit an AP registration request flagthrough a beacon frame, an authentication frame or an association frameother than the probe frame. Transmitting the AP registration requestflag through a probe frame and a beacon frame may correspond to anuntrusted method because a request for AP registration is transmitted toan unspecific, unauthenticated device. Transmitting an AP registrationrequest flag through an authentication frame or an association frame maycorrespond to a trusted method because a request for AP registration istransmitted to an authenticated specific device. However, if a probeframe is transmitted in a unicast manner and is transmitted afterauthenticated, this may correspond to a trusted method.

In step S110, the multi-RAT device authorizes the AP registrationrequest received from the AP. If the multi-RAT device authorizes the APregistration request while in an idle mode, the multi-RAT device mayshift to an active mode.

If the multi-RAT device does not authorize the AP registration request,the multi-RAT device may transmit an AP registration result parameter ora newly defined AP registration response frame to the AP. At this time,the AP registration result parameter or AP registration response framemay include a result (‘failure’) of the AP registration request andcause for the failure. The cause for the multi-RAT device not toauthorize the AP registration request may be when cannot support therequest from the AP (‘not support’) or when the multi-RAT device and thecellular system are not in the proper state for authorizing the APregistration request and thus cannot fulfill the request from the AP(‘not suitable’).

If the multi-RAT device authorizes the AP's registration request, instep S120, the multi-RAT device determines whether the corresponding APis included in a latest valid AP list. That is, if the multi-RAT devicehas a latest valid AP list that has been received from the cellularnode, the multi-RAT device identifies whether the AP that has requestedregistration is included in the AP list. Accordingly, the multi-RATdevice may grasp whether the cellular node already manages the AP thathas requested registration. If the multi-RAT device does not have an APlist, or if the multi-RAT device has an AP list but the AP list isinvalid, the multi-RAT device may transmit a request for a latest validAP list to the cellular node.

If the AP that has requested registration is included in a latest validAP list, the multi-RAT device may transmit an AP registration resultparameter or a newly defined AP registration response frame to the AP.At this time, the AP registration result parameter or AP registrationresponse frame may include a result (‘already registered’) of the APregistration request.

If the AP is not included in the latest valid AP list, in step S130, themulti-RAT device transmits an AP registration request message to thecellular node. The AP registration request message may include APinformation such as a MAC address of the AP, SSID of the AP, whetheronly a limited user may use the AP (closed subscriber group(CSG)/password or open subscriber group (OSG)), position of the AP,homogeneous ESS ID (HESSID) of the AP, information on the frequencychannel used by the AP (operating class or channel number), which havebeen obtained through a Wi-Fi scanning procedure. If the cellular nodeis a base station, the AP registration request message may be a radioresource control (RRC) message. If the cellular node is an MME, the APregistration request message may be a non-access stratum (NAS) message.

Upon receiving the AP registration request message from the multi-RATdevice, the cellular node stores the AP information included in the APregistration request message. The cellular node may be implicitly awareof which coverage a corresponding AP belongs to according to thetransmission path of the AP registration request message. For example,if the cellular node is an MME, the AP registration request message istransmitted from the multi-RAT device to an eNB that provides a servingcell of the multi-RAT device, and the MME may receive the APregistration request message from the eNB. Since the MME has receivedthe AP registration request message from the eNB, the MME may determinethat the corresponding AP is within the coverage of the eNB.

In step S131, the cellular node transmits an AP registration responsemessage to the multi-RAT device as a response to the AP registrationrequest message. The AP registration response message includes a resultof the AP's registration request. For example, the result of 0x00denotes ‘already registered,’ the result of 0x01 denotes ‘success,’ andthe result of 0x02 denotes ‘failure.’

Further, the AP registration response message may include a list ofregistered APs. For example, if the AP that has transmitted a requestfor registration has been already registered, the cellular node maydetermine that the multi-RAT device does not have a latest valid APlist. Accordingly, by transmitting an AP registration response messageincluding an AP list to the multi-RAT device, the multi-RAT device maybe rendered to update the AP list. Or, the cellular node may transmit aregistered APs list to a plurality of multi-RAT devices in a broadcastor unicast manner.

If the multi-RAT device receives, within a predetermined time, anacknowledgement of the AP registration request message transmitted instep S130 or the AP registration response message transmitted from thecellular node in step S131, in step S140, the multi-RAT device transmitsan association response frame to the AP. The association response framemay include an AP registration result parameter. The AP registrationresult parameter indicates a response to the AP registration request.That is, the AP registration result parameter includes a result for theAP's registration request and cause for the result. For example, if theresult for the AP registration request is 0x00, this denotes ‘alreadyregistered,’ if the result is 0x01, this denotes ‘success,’ and if theresult is 0x02, this denotes ‘failure.’ In the embodiment described inFIG. 7, the result for the AP registration request denotes ‘success.’Meanwhile, an existing probe frame or authentication frame, instead ofthe association frame, may be used for transmitting an AP registrationresult parameter.

The cause for the result of the AP registration request may be onemainly for when the result is ‘failure.’. That is, if the result is‘already registered’ or ‘success,’ the cause for the AP registrationrequest result may be omitted or set as a meaningless value. Examples ofthe cause for the AP registration request result are as follows.

-   -   Not support: denotes that the multi-RAT device cannot support        the AP's registration request.    -   Not suitable: denotes that the multi-RAT device and the cellular        system are not in the proper state for authorizing the AP's        registration request so that they cannot fulfill the AP        registration request.    -   Not response with retry procedure: denotes that, when failing to        receive an acknowledgement the AP registration request message        transmitted from the multi-RAT device in step S130 or failing to        receive the AP registration response message transmitted from        the cellular node in step S131 within a predetermined time, the        multi-RAT device performs a re-transmission procedure therefor.    -   Not response without retry procedure: denotes that, when failing        to receive an acknowledgement the AP registration request        message transmitted from the multi-RAT device in step S130 or        failing to receive the AP registration response message        transmitted from the cellular node in step S131 within a        predetermined time, the multi-RAT device does not perform a        re-transmission procedure therefor.    -   Not registered: denotes that a result of response of the        cellular node to the AP registration request is ‘failure.’

If the multi-RAT device fails to receive, from the cellular node, anacknowledgement of the AP registration request message or the APregistration response message within a predetermined time, the multi-RATdevice may transmit the AP registration result parameter to the AP,thereby performing a retransmission procedure. At this time, the APregistration result parameter may include a result of the APregistration request (‘failure’) and cause for the result (‘not responsewith retry procedure’). In case of failing to receive, within apredetermined time, an acknowledgement of the AP registration requestmessage or the AP registration response message from the cellular nodedespite attempting the retransmission procedure by the maximum number oftimes of retransmission, the multi-RAT device may transmit the APregistration result parameter to the AP. At this time, the APregistration result parameter may include a result of the APregistration request (‘failure’) and cause for the result (‘not responsewithout retry procedure’).

Upon receiving the AP registration result parameter whose result is‘already registered’ or ‘success’ from the multi-RAT device, the AP maydetermine that its request has been successfully done. Upon receivingthe AP registration result parameter with a result of ‘failure’ andcause for the result of ‘Not support,’ ‘Not suitable,’ or ‘Not responsewithout retry procedure’ from the multi-RAT device, the AP mayretransmit a request for AP registration to another multi-RAT device.Upon receiving the AP registration result parameter with a result of‘failure’ and cause for result of ‘Not response with retry procedure,’from the multi-RAT device, the AP may await an additional response fromthe corresponding multi-RAT device. Upon receiving the AP registrationresult parameter with a result of ‘failure’ and cause for result of ‘Notregistered,’ from the multi-RAT device, the AP may stop transmitting arequest for AP registration.

Or, the multi-RAT device may transmit a newly defined AP registrationresponse frame, instead of the association response frame to the AP. Instep S150, the multi-RAT device determines whether the corresponding APis included in the latest valid AP list. This is the same as step S120.If the AP is not included in the latest valid AP list, in step S160, themulti-RAT device transmits an AP registration request message to thecellular node. This is the same as step S130. In step S131, the cellularnode transmits an AP registration response message to the multi-RATdevice as a response to the AP registration request message. This is thesame as step S131.

If the multi-RAT device receives an acknowledgement of the APregistration request message transmitted in step S160 or receives the APregistration response message transmitted from the cellular node in stepS161 within a predetermined time, in step S170, the multi-RAT devicetransmits the AP registration response frame to the AP. The APregistration response frame indicates a response to the AP registrationrequest. That is, the AP registration response frame includes a resultof the AP registration request and cause for the result. For example,the result of the AP registration request being 0x00 denotes ‘alreadyregistered,’ the result being 0x01 denotes ‘success,’ and the resultbeing 0x02 denotes ‘failure.’ In the embodiment described in FIG. 7, theresult of the AP registration request denotes ‘success.’

The cause for the result of the AP registration request may be onemainly for when the result is ‘failure.’ That is, if the result is‘already registered’ or ‘success,’ the cause for result of the APregistration request may be omitted or may be set as a meaninglessvalue. Examples of the cause for the result of AP registration requestare as follows.

-   -   Not support: denotes that the multi-RAT device cannot support        the AP's registration request.    -   Not suitable: denotes that the multi-RAT device and the cellular        system are not in the proper state for authorizing the AP's        registration request so that they cannot fulfill the AP        registration request.    -   Not response with retry procedure: denotes that, when failing to        receive an acknowledgement the AP registration request message        transmitted from the multi-RAT device in step S130 or failing to        receive the AP registration response message transmitted from        the cellular node in step S131 within a predetermined time, the        multi-RAT device performs a re-transmission procedure therefor.    -   Not response without retry procedure: denotes that, when failing        to receive an acknowledgement the AP registration request        message transmitted from the multi-RAT device in step S130 or        failing to receive the AP registration response message        transmitted from the cellular node in step S131 within a        predetermined time, the multi-RAT device does not perform a        re-transmission procedure therefor.    -   Not registered: denotes that a result of response of the        cellular node to the AP registration request is ‘failure.’

If the multi-RAT device fails to receive an acknowledgment of the APregistration request message or fails to receive the AP registrationresponse message from the cellular node within a predetermined time, themulti-RAT device transmits the AP registration response frame to the AP,thereby performing a retransmission procedure. At this time, the APregistration response frame may include a result of the AP registrationrequest (‘failure’) and cause for the result (‘not response with retryprocedure’). In case of failing to receive an acknowledgement of the APregistration request message or failing to receive the AP registrationresponse message from the cellular node within a predetermined timedespite attempting the retransmission procedure by the maximum number oftimes of retransmission, the multi-RAT device may transmit the APregistration response frame to the AP. At this time, the AP registrationresponse frame may include a result of the AP registration request(‘failure’) and cause for the result (‘not response without retryprocedure’).

Upon receiving the AP registration response frame whose result is‘already registered’ or ‘success’ from the multi-RAT device, the AP maydetermine that its request has been successfully done. Upon receivingthe AP registration response frame with a result of ‘failure’ and causefor the result of ‘Not support,’ ‘Not suitable,’ or ‘Not responsewithout retry procedure’ from the multi-RAT device, the AP mayretransmit a request for AP registration to another multi-RAT device.Upon receiving the AP registration response frame with a result of‘failure’ and cause for result of ‘Not response with retry procedure,’from the multi-RAT device, the AP may await an additional response fromthe corresponding multi-RAT device. Upon receiving the AP registrationresponse frame with a result of ‘failure’ and cause for result of ‘Notregistered,’ from the multi-RAT device, the AP may stop transmitting arequest for AP registration.

FIG. 8 shows an AP registration method according to another embodimentof the present invention. In the embodiment described in FIG. 8, an APregistration method is described where an AP defines a new Wi-Fi systemframe and requests its registration. As a new Wi-Fi system frame for APregistration, an AP registration request/response frame may be defined.

In step S200, the AP transmits an AP registration request frame to amulti-RAT device to request from the multi-RAT device, which receivesthe AP registration request frame, to register the AP in a cellularnode. The AP registration request frame is a frame newly defined forrequesting registration of the AP in the cellular node. The APregistration request frame is merely an example, and other frames forrequesting AP registration may be defined as well.

FIG. 9 shows an example of an AP registration request frame structureaccording to an embodiment of the present invention.

Referring to FIG. 9, the AP registration request frame may be used, asis, in the form of an existing management frame as standardized in IEEE802.11. In other words, the AP registration request frame, like the IEEE802.11 management frame, may include a frame control field, aduration/ID field, an address 1 field, an address 2 field, an address 3field, a sequence control field, an HT control field, a frame bodyfield, and an FCS field.

Further, the frame control field may include a protocol versionsubfield, a type subfield, a subtype subfield, a to DS subfield, a fromDS subfield, a more fragments subfield, a retry subfield, a powermanagement subfield, a more data subfield, a protected frame subfield,and an order subfield. Table 2 represents the type subfield and subtypesubfield in the frame control field.

TABLE 2 Type value Type Subtype value Subtype B3 b2 description b7 b6 b4b4 description 00 Data 1101 Reserved 01 Data 1110 QoS CF-Poll (no data)10 Data 1111 QoS CF-Ack + CF-Poll (no data) 11 Reserved 0000-1100Reserved

In order to represent that the corresponding frame is an AP registrationrequest frame or an AP registration response frame, reserved values ofthe type subfield and subtype subfield may be used. For example, thereserved value of the type subfield being 0b11 may denote inter-RATworking management. Further, the reserved value of the subtype subfieldbeing 0b0010 may denote an AP registration request frame, and likewise,the reserved value of the subtype subfield being 0b0011 may denote an APregistration response frame.

Further, the AP registration request response frame may further includeinformation on whether a re-transmission procedure request is made asthe AP registration request fails.

Referring to FIG. 8 again, in step S210, the multi-RAT device authorizesthe AP registration request received from the AP. If the multi-RATdevice is in an idle mode when authorizing the AP registration request,the multi-RAT device may shift to an active mode.

If the multi-RAT device does not authorize the AP registration request,the multi-RAT device may transmit a newly defined AP registrationresponse frame to the AP. At this time, the AP registration responseframe may include a result (‘failure’) of the AP registration requestand cause for the result. The cause for the multi-RAT device not toauthorize the AP registration request may be when cannot support therequest from the AP (‘not support’) or when the multi-RAT device and thecellular system are not in the proper state for authorizing the APregistration request and thus cannot fulfill the request from the AP(‘not suitable’).

If the multi-RAT device authorizes the AP's registration request, instep S220, the multi-RAT device determines whether the corresponding APis included in a latest valid AP list. That is, in case the multi-RATdevice has a latest valid AP list that has been received from a cellularnode, the multi-RAT device identifies whether the AP that has requestedregistration is included in the AP list. Accordingly, the multi-RATdevice may grasp whether the cellular node already manages the AP thathas requested registration. If the multi-RAT device does not have an APlist, or if the multi-RAT device has an AP list but the AP list isinvalid, the multi-RAT device may transmit a request for a latest validAP list to the cellular node.

If the AP that has requested registration is included in a latest validAP list, the multi-RAT device may transmit a newly defined APregistration response frame to the AP. At this time, the AP registrationresponse frame may include a result (‘already registered’) of the APregistration request.

If the AP is not included in the latest valid AP list, in step S230, themulti-RAT device transmits an AP registration request message to thecellular node. The AP registration request message may include APinformation such as the MAC address of the AP, SSID of the AP, whetheronly a limited user may use the AP (CSG/password or OSG), position ofthe AP, HESSID of the AP, information on the frequency channel used bythe AP (operating class or channel number), which has been obtainedthrough a Wi-Fi scanning procedure. If the cellular node is an eNB, theAP registration request message may be an RRC message. In case thecellular node is an MME, the AP registration request message may be aNAS message.

Upon receiving the AP registration request message from the multi-RATdevice, the cellular node stores the AP information included in the APregistration request message. The cellular node may be implicitly awareof which coverage the corresponding AP belongs to according to thetransmission path of the AP registration request message. For example,in case the cellular node is an MME, the AP registration request messageis transmitted from the multi-RAT device to an eNB that provides aserving cell of the multi-RAT device, and the MME may receive the APregistration request message from the eNB. Since the MME has receivedthe AP registration request message from the eNB, the MME may determinethat the corresponding AP is within the coverage of the eNB.

In step S231, the cellular node transmits an AP registration responsemessage to the multi-RAT device as a response to the AP registrationrequest message. The AP registration response message includes a resultof the AP's registration request. For example, the result of 0x00denotes ‘already registered,’ the result of 0x01 denotes ‘success,’ andthe result of 0x02 denotes ‘failure.’

Further, the AP registration response message may include a list ofregistered APs. For example, if the AP that has transmitted a requestfor registration has been already registered, the cellular node maydetermine that the multi-RAT device does not have a latest valid APlist. Accordingly, by transmitting an AP registration response messageincluding an AP list to the multi-RAT device, the multi-RAT device maybe rendered to update the AP list. Or, the cellular node may transmit aregistered APs list to a plurality of multi-RAT devices in a broadcastor unicast manner.

If the multi-RAT device receives an acknowledgement of the APregistration request message transmitted in step S230 or receives the APregistration response message transmitted from the cellular node in stepS231 within a predetermined time, in step S240, the multi-RAT devicetransmits the AP registration response frame to the AP. The APregistration response frame denotes a response to the AP registrationrequest. That is, the AP registration response frame includes a resultof the AP registration request and cause for the result. For example,the result of the AP registration request being 0x00 denotes ‘alreadyregistered,’ the result of 0x01 denotes ‘success,’ and the result of0x02 denotes ‘failure.’ In the embodiment described in FIG. 8, theresult of the AP registration request denotes ‘success.’

The cause for the result of the AP registration request may be onemainly for when the result is ‘failure.’ That is, if the result is‘already registered’ or ‘success,’ the cause for result of the APregistration request may be omitted or may be set as a meaninglessvalue. The cause for the result of AP registration request may be anyone of ‘not support’, ‘not suitable’, ‘not response with retryprocedure’, ‘not response without retry procedure’, and ‘notregistered.’

In case the multi-RAT device fails to receive an acknowledgment of theAP registration request message or fails to receive the AP registrationresponse message from the cellular node within a predetermined time, themulti-RAT device transmits the AP registration response frame to the AP,thereby performing a retransmission procedure. At this time, the APregistration response frame may include a result of the AP registrationrequest (‘failure’) and cause for the result (‘not response with retryprocedure’). In case of failing to receive an acknowledgment of the APregistration request message or failing to receive the AP registrationresponse message from the cellular node within a predetermined timedespite attempting the retransmission procedure by the maximum number oftimes of retransmission, the multi-RAT device may transmit the APregistration response frame to the AP. At this time, the AP registrationresponse frame may include a result of the AP registration request(‘failure’) and cause for the result (‘ot response without retryprocedure’).

Upon receiving the AP registration response frame whose result is‘already registered’ or ‘success’ from the multi-RAT device, the AP maydetermine that its request has been successfully done. Upon receivingthe AP registration response frame with a result of ‘failure’ and causefor the result of ‘not support,’ ‘not suitable,’ or ‘not responsewithout retry procedure’ from the multi-RAT device, the AP mayretransmit a request for AP registration to another multi-RAT device.Upon receiving the AP registration response frame with a result of‘failure’ and cause for result of ‘not response with retry procedure,’from the multi-RAT device, the AP may await an additional response fromthe corresponding multi-RAT device. Upon receiving the AP registrationresponse frame with a result of ‘failure’ and cause for result of ‘notregistered,’ from the multi-RAT device, the AP may stop transmitting arequest for AP registration.

FIG. 10 shows an AP registration method according to another embodimentof the present invention. In the embodiment described in FIG. 10, an APregistration method is described where an AP defines a new independentmessage, which is independent with a Wi-Fi system, and requests itsregistration. The AP registration request/response transmitted from theAP is encapsulated in a Wi-Fi system frame and is then transmitted.

In step S300, the AP transmits an encapsulated frame including an APregistration request to the multi-RAT device. The AP registrationrequest may be an AP registration request message. The AP registrationrequest message may be defined by a protocol scheme with the cellularnode. That is, the AP registration request message is encapsulated inthe frame body field of an IEEE 802.11 frame and is then transmitted.Accordingly, the AP registration request message is definedindependently from the Wi-Fi system frame. The AP registration requestmessage may include AP information such as the MAC address of the AP,SSID of the AP, whether only a limited user may use the AP (CSG/passwordor OSG), position of the AP, HESSID of the AP, information on thefrequency channel used by the AP (operating class or channel number),which has been obtained through a Wi-Fi scanning procedure. Further, byusing the type subfield or subtype subfield in the frame control fieldor the address field in the MAC header of the frame including theencapsulated AP registration request message, it may be notified to themulti-RAT device that the corresponding frame should be transmitted tothe cellular node. Further, the AP registration request message mayfurther include information on whether a re-transmission procedurerequest is made as the AP registration request fails.

In step S310, the multi-RAT device authorizes the AP registrationrequest received from the AP. This means that the multi-RAT device maydeliver (forward) the frame received from the AP to the cellular node.If the multi-RAT device is in an idle mode when authorizing the APregistration request, the multi-RAT device may shift to an active mode.

If the multi-RAT device does not authorize the AP registration request,the multi-RAT device may transmit a frame having a newly defined APregistration response message encapsulated therein to the AP. At thistime, the AP registration response message may include a result(‘failure’) of the AP registration request and cause for the failure.The cause for the multi-RAT device not to authorize the AP registrationrequest may be when cannot support the request from the AP (‘notsupport’) or when the multi-RAT device and the cellular system are notin the proper state for authorizing the AP registration request and thuscannot fulfill the request from the AP (‘not suitable’). At this time,the AP may retransmit a request for AP registration to other multi-RATdevices.

If the type subfield or subtype subfield in the frame control field orthe address field in the MAC header in the received frame indicate thatthe frame is one that should be transmitted to the cellular node, instep S320, the multi-RAT device transmits the AP registration requestmessage included in the body of the corresponding frame to the cellularnode.

Upon receiving the AP registration request message from the multi-RATdevice, the cellular node stores the AP information included in the APregistration request message. The cellular node may be implicitly awareof which coverage the corresponding AP belongs to according to thetransmission path of the AP registration request message. For example,if the cellular node is an MME, the AP registration request message istransmitted from the multi-RAT device to an eNB that provides a servingcell of the multi-RAT device, and the MME may receive the APregistration request message from the eNB. Since the MME has receivedthe AP registration request message from the eNB, the MME may determinethat the corresponding AP is within the coverage of the eNB.

In step S321, the cellular node transmits an AP registration responsemessage to the multi-RAT device as a response to the AP registrationrequest message. The AP registration response message includes a resultof the AP registration request. For example, the result of 0x00 denotes‘already registered,’ the result of 0x01 denotes ‘success,’ and theresult of 0x02 denotes ‘failure.’ Further, the cellular node may informthe multi-RAT device that the AP registration response message is amessage that should be transmitted to the AP.

If the received AP registration response message is a message thatshould be transmitted to the AP, in step S340, the multi-RAT devicetransmits an encapsulated frame including the AP registration responsemessage to the AP.

Upon receiving the frame including the AP registration response messagewith a result of ‘already registered’ or ‘success’ from the multi-RATdevice, the AP may determine that its request has been successfullydone. Upon receiving the frame including the AP registration responsemessage with a result of ‘failure’ or failing to receive a responsewithin a predetermined time from the multi-RAT device, the AP mayretransmit a request for AP registration to the same or other multi-RATdevices.

Hereinafter, an AP registration procedure which is initiated by ageneral device according to an embodiment of the present invention isdescribed.

FIG. 11 shows an AP registration method according to another embodimentof the present invention. In the embodiment described in FIG. 11, thegeneral device access to a Wi-Fi system, and accordingly, automaticallyperforms AP registration. That is, if the general device discovers an APthrough scanning, the general device transmits a request for APregistration to a cellular node.

In step S400, the AP transmits a beacon frame or probe frame. Themulti-RAT device may detect the beacon frame or probe frame transmittedfrom the AP by scanning. If the multi-RAT device is in an idle mode, themulti-RAT device may shift to an active mode.

In step S401, the multi-RAT device requests AP registration bytransmitting an AP registration request message to the cellular node.The AP registration request message may include AP information such asthe MAC address of the AP, SSID of the AP, whether only a limited usermay use the AP (CSG/password or OSG), position of the AP, HESSID of theAP, information on the frequency channel used by the AP (operating classor channel number), which has been obtained through a Wi-Fi scanningprocedure.

Upon receiving the AP registration request message from the multi-RATdevice, the cellular node stores the AP information included in the APregistration request message. The cellular node may be implicitly awareof which coverage the corresponding AP belongs to according to thetransmission path of the AP registration request message. For example,if the cellular node is an MME, the AP registration request message istransmitted from the multi-RAT device to an eNB that provides a servingcell of the multi-RAT device, and the MME may receive the APregistration request message from the eNB. Since the MME has receivedthe AP registration request message from the eNB, the MME may determinethat the corresponding AP is within the coverage of the eNB.

In step S411, the cellular node transmits the AP registration responsemessage to the multi-RAT device as a response to the AP registrationrequest message. The AP registration response message includes a resultof the AP registration request. For example, the result of 0x00 denotes‘already registered,’ the result of 0x01 denotes ‘success,’ and theresult of 0x02 denotes ‘failure.’ In the embodiment described in FIG.11, the result of AP registration request denotes ‘success.’

Further, the AP registration response message may include a list ofregistered APs. For example, if an AP that has transmitted a request forregistration has been already registered, the cellular node maydetermine that the multi-RAT device does not have a latest valid APlist. Accordingly, by transmitting an AP registration response messageincluding an AP list to the multi-RAT device, the multi-RAT device maybe rendered to update the AP list. Or, the cellular node may transmit aregistered APs list to a plurality of multi-RAT devices in a broadcastor unicast manner.

Upon receiving the AP registration response message with a result of‘already registered’ or ‘success’ from the cellular node within apredetermined time, the multi-RAT device may determine that the APregistration has been successfully done. Upon receiving the APregistration response message with a result of ‘failure’ from thecellular node within a predetermined time, the multi-RAT device maydetermine that the AP registration has failed. When failing to receivethe AP registration response message from the cellular node within apredetermined time, the multi-RAT device may perform retransmissionprocedure by the maximum number of times for retransmission.

FIG. 12 shows an AP registration method according to another embodimentof the present invention. In the embodiment described in FIG. 12, amethod is described where a general device performs AP registrationbased on an AP list received from a cellular node. If the general devicehas a latest valid AP list received from the cellular node, the generaldevice may identify whether an AP discovered through scanning isincluded in the AP list. If there is no latest valid AP list receivedfrom the cellular node, the general device may transmit a request for alatest valid AP list to the cellular node. The general device maytransmit a request for registering the corresponding AP to the cellularnode only when the corresponding AP is not included in the latest validAP list.

In step S500, the AP transmits a beacon frame or a probe frame. Themulti-RAT device may detect the beacon frame or probe frame transmittedfrom the AP by scanning. If the multi-RAT device is in an idle mode, themulti-RAT device may shift to an active mode.

In step S510, the multi-RAT device may transmit a request for a latestvalid AP list to the cellular node. The multi-RAT device may transmit arequest for the latest valid AP list only when the multi-RAT devicefails to receive the latest valid AP list from the cellular node. Instep S511, the cellular node transmits the latest valid AP list to themulti-RAT device.

In step S520, the multi-RAT device determines whether the correspondingAP discovered through scanning is included in the latest valid AP list.That is, the multi-RAT device may verify whether the corresponding AP,discovered by scanning, is already managed by the cellular node. If theAP is included in the latest valid AP list, the multi-RAT device doesnot request registration of the AP.

If the AP is not included in the latest valid AP list, in step S530, themulti-RAT device requests registration of the AP by transmitting an APregistration request message to the cellular node. The AP registrationrequest message may include AP information such as the MAC address ofthe AP, SSID of the AP, whether only a limited user may use the AP(CSG/password or OSG), position of the AP, HESSID of the AP, informationon the frequency channel used by the AP (operating class or channelnumber), which has been obtained through a Wi-Fi scanning procedure.

Upon receiving the AP registration request message from the multi-RATdevice, the cellular node stores the AP information included in the APregistration request message. The cellular node may be implicitly awareof which coverage the corresponding AP belongs to according to thetransmission path of the AP registration request message. For example,in case the cellular node is an MME, the AP registration request messageis transmitted from the multi-RAT device to an eNB that provides aserving cell of the multi-RAT device, and the MME may receive the APregistration request message from the eNB. Since the MME has receivedthe AP registration request message from the eNB, the MME may determinethat the corresponding AP is within the coverage of the eNB.

In step S531, the cellular node transmits an AP registration responsemessage to the multi-RAT device as a response to the AP registrationrequest message. The AP registration response message includes a resultof the AP registration request. For example, the result of 0x00 denotes‘already registered,’ the result of 0x01 denotes ‘success,’ and theresult of 0x02 denotes ‘failure.’ In the embodiment described inconnection with FIG. 12, the result of the AP registration requestdenotes ‘success.’

Further, the AP registration response message may include a list ofregistered APs. For example, if an AP that has transmitted a request forregistration has been already registered, the cellular node maydetermine that the multi-RAT device does not have a latest valid APlist. Accordingly, by transmitting an AP registration response messageincluding an AP list to the multi-RAT device, the multi-RAT device maybe rendered to update the AP list. Or, the cellular node may transmit aregistered APs list to a plurality of multi-RAT devices in a broadcastor unicast manner.

Upon receiving the AP registration response message with a result of‘already registered’ or ‘success’ from the cellular node within apredetermined time, the multi-RAT device may determine that the APregistration has been successfully done. Upon receiving the APregistration response message with a result of ‘failure’ from thecellular node within a predetermined time, the multi-RAT device maydetermine that the AP registration has failed. Upon failing to receivethe AP registration response message from the cellular node within apredetermined time, the multi-RAT device may perform retransmissionprocedure by the maximum number of times for retransmission.

Hereinafter, an AP registration procedure which is initiated by acellular node according to an embodiment of the present invention isdescribed. The AP registration procedure initiated by the cellular nodemay be described in addition to the AP registration procedure that isinitiated by a general device as described above.

In case of AP automatic registration according to Wi-Fi access, when ageneral device that has received a heterogeneous network informationrequest from the cellular node discovers an AP through scanning, thegeneral device may transmit a request for registration of thecorresponding AP to the cellular node. In case of AP registration basedon a latest valid AP list received from the cellular node, when thegeneral device that has received a heterogeneous information requestfrom the cellular node has a latest valid AP list, the general devicemay verify whether the AP discovered through scanning is included in anAP list. If there is no latest valid AP list received from the cellularnode, the general device may transmit a request for a latest valid APlist to the cellular node. The general device may transmit a request forregistration of the AP to the general device only when the AP is notincluded in the latest valid AP list. Or, when receiving a message withthe latest valid AP list and AP registration flag set as 1 from thecellular node, the general device may identify whether the AP discoveredthrough scanning is included in the AP list. The general device maytransmit a request for registration of the AP to the cellular node onlywhen the AP is not included in the latest valid AP list.

Hereinafter, an AP information update configuration is described.

A cellular node may inform an update configuration on an AP informationthrough an AP registration response message. The update configurationmay represent an update scheme. The update scheme may be generallyclassified into periodic transmission and aperiodic transmission. If theupdate scheme is periodic transmission, the cellular node may transmitparameters such as update transmission period through an AP registrationresponse message. The AP or multi-RAT device may periodically transmitchanged AP information to the cellular node. If the update scheme isaperiodic transmission, the AP or multi-RAT device may transmit thechanged AP information to the cellular node only when update conditionsare met. The changed AP information may be transmitted through an APinformation update request/response message.

The update conditions may be associated with a change in Wi-Fi systeminformation. For example, when at least one of AP's MAC address, AP'sSSID, whether the AP is used only by a limited user (CSG/password orOSG), AP's HESSID, information on frequency channel used by the AP(operating class, channel number, etc.), power ON/OFF, power ONduration, power OFF duration, and AP's position is changed, the updateconditions may be satisfied. The power ON/OFF is a parameter to notifythe power ON/OFF state of an AP already registered in the cellular node.For example, if some AP tries to power off or multi-RAT deviceexplicitly or implicitly recognizes the situation where the AP's topower off, the corresponding information may be updated in the cellularnode. A re-registration procedure may be performed when powered-off APpowers back on. Further, if power is temporarily off, for example, dueto software upgrade, the power-off duration may be additionallyinformed, so that the cellular node may be aware of the time when the APis re-powered. At this time, no re-registration procedure may be neededfor the AP.

FIG. 13 is a block diagram showing wireless communication system toimplement an embodiment of the present invention.

A general device 800 includes a processor 810, a memory 820, and a radiofrequency (RF) unit 830. The processor 810 may be configured toimplement proposed functions, procedures, and/or methods in thisdescription. Layers of the radio interface protocol may be implementedin the processor 810. The memory 820 is operatively coupled with theprocessor 810 and stores a variety of information to operate theprocessor 810. The RF unit 830 is operatively coupled with the processor810, and transmits and/or receives a radio signal.

An AP or cellular node 900 may include a processor 910, a memory 920 anda RF unit 930. The processor 910 may be configured to implement proposedfunctions, procedures and/or methods described in this description.Layers of the radio interface protocol may be implemented in theprocessor 910. The memory 920 is operatively coupled with the processor910 and stores a variety of information to operate the processor 910.The RF unit 930 is operatively coupled with the processor 910, andtransmits and/or receives a radio signal.

The processors 810, 910 may include application-specific integratedcircuit (ASIC), other chipset, logic circuit and/or data processingdevice. The memories 820, 920 may include read-only memory (ROM), randomaccess memory (RAM), flash memory, memory card, storage medium and/orother storage device. The RF units 830, 930 may include basebandcircuitry to process radio frequency signals. When the embodiments areimplemented in software, the techniques described herein can beimplemented with modules (e.g., procedures, functions, and so on) thatperform the functions described herein. The modules can be stored inmemories 820, 920 and executed by processors 810, 910. The memories 820,920 can be implemented within the processors 810, 910 or external to theprocessors 810, 910 in which case those can be communicatively coupledto the processors 810, 910 via various means as is known in the art.

In view of the exemplary systems described herein, methodologies thatmay be implemented in accordance with the disclosed subject matter havebeen described with reference to several flow diagrams. While forpurposed of simplicity, the methodologies are shown and described as aseries of steps or blocks, it is to be understood and appreciated thatthe claimed subject matter is not limited by the order of the steps orblocks, as some steps may occur in different orders or concurrently withother steps from what is depicted and described herein. Moreover, oneskilled in the art would understand that the steps illustrated in theflow diagram are not exclusive and other steps may be included or one ormore of the steps in the example flow diagram may be deleted withoutaffecting the scope and spirit of the present disclosure.

What is claimed is:
 1. A method of registering, by a multi radio accesstechnology (RAT) device supporting a plurality of RATs, an entity of asecondary RAT system in a management device of a primary RAT system in awireless communication system, the method comprising: receiving arequest for registration of an entity of a secondary RAT system from theentity of the secondary RAT system; if the request for registration isauthorized, determining whether the entity of the secondary RAT systemis included in a list of entities of the secondary RAT system registeredin a management device of a primary RAT system; if it is determined thatthe entity of the secondary RAT system is not included in the list,transmitting a registration request message including information on theentity of the secondary RAT system to the management device of theprimary RAT system; receiving a registration response message includinga result of the request for registration of the entity of the secondaryRAT system from the management device of the primary RAT system; andtransmitting a registration result parameter including the result of theregistration of the entity of the secondary RAT system to the entity ofthe secondary RAT system.
 2. The method of claim 1, wherein the requestfor registration of the entity of the secondary RAT system is an accesspoint (AP) registration request flag included in a beacon frame, a proberesponse frame, an authentication response frame, or an associationresponse frame.
 3. The method of claim 1, wherein the request forregistration of the entity of the secondary RAT system is a newlydefined AP registration request frame.
 4. The method of claim 1, whereinthe information on the entity of the secondary RAT system includes atleast one of a media access control (MAC) address of the entity of thesecondary RAT system, a service set identifier (SSID) of the entity ofthe secondary RAT system, a position of the entity of the secondary RATsystem, an homogeneous extended service set ID (HESSID) of the entity ofthe secondary RAT system, whether of the entity of the secondary RATsystem can be used by a limited user, or information on a frequencychannel used by the entity of the secondary RAT system.
 5. The method ofclaim 1, wherein the result of the request for registration of theentity of the secondary RAT system is one of ‘already registered,’‘success,’ or ‘failure’.
 6. The method of claim 5, wherein if the resultof the request for registration of the entity of the secondary RATsystem is ‘failure,’ the registration result parameter further includescause for the result of the request for registration.
 7. The method ofclaim 1, wherein the primary RAT system is a cellular system, andwherein the management device of the primary RAT system is one of aneNodeB (eNB), a mobility management entity (MME), or a new entity of thecellular system.
 8. The method of claim 1, wherein the secondary RATsystem is a Wi-Fi system, and wherein the entity of the secondary RATsystem is an AP.
 9. A method of registering, by a multi radio accesstechnology (RAT) device supporting a plurality of RATs, an entity of asecondary RAT system in a management device of a primary RAT system in awireless communication system, the method comprising: receiving a firstframe from an entity of a secondary RAT system, wherein a request forregistration of the entity of the secondary RAT system and informationon the entity of the secondary RAT system are encapsulated in the firstframe; transmitting a registration request message including the requestfor registration of the entity of the secondary RAT system and theinformation on the entity of the secondary RAT system to a managementdevice of a primary RAT system; receiving a registration responsemessage including a result of the request for registration of the entityof the secondary RAT system from the management device of the primaryRAT system; and transmitting a second frame to the entity of thesecondary RAT system, wherein the result of the request for registrationof the entity of the secondary RAT system is encapsulated in the secondframe.
 10. The method of claim 9, wherein the information on the entityof the secondary RAT system includes at least one of a media accesscontrol (MAC) address of the entity of the secondary RAT system, aservice set identifier (SSID) of the entity of the secondary RAT system,a position of the entity of the secondary RAT system, an homogeneousextended service set ID (HESSID) of the entity of the secondary RATsystem, whether of the entity of the secondary RAT system can be used bya limited user, or information on a frequency channel used by the entityof the secondary RAT system.
 11. The method of claim 9, wherein thefirst frame includes a field indicating that the first frame istransmitted to the management device of the primary RAT system.
 12. Themethod of claim 9, wherein the registration response message indicatesthat the registration response message is transmitted to the entity ofthe secondary RAT system.
 13. A method of registering, by a multi radioaccess technology (RAT) device supporting a plurality of RATs, an entityof a secondary RAT system in a management device of a primary RAT systemin a wireless communication system, the method comprising: discoveringan entity of a secondary RAT system through scanning; transmitting aregistration request message including information on the entity of thesecondary RAT system to a management device of a primary RAT system; andreceiving a registration response message including a result of therequest for registration of the entity of the secondary RAT system fromthe management device of the primary RAT system.
 14. The method of claim13, wherein the information on the entity of the secondary RAT systemincludes at least one of a media access control (MAC) address of theentity of the secondary RAT system, a service set identifier (SSID) ofthe entity of the secondary RAT system, a position of the entity of thesecondary RAT system, an homogeneous extended service set ID (HESSID) ofthe entity of the secondary RAT system, whether of the entity of thesecondary RAT system can be used by a limited user, or information on afrequency channel used by the entity of the secondary RAT system. 15.The method of claim 13, further comprising: transmitting a request for alist of entities of a secondary RAT system registered in the managementdevice of the primary RAT system to the management device of the primaryRAT system.